A backlight described in Patent Document 1 described below has been known as an example of a backlight used for a typical liquid crystal display device. A planar light source as the backlight described in Patent Document 1 includes LEDs configured to emit blue light, a wavelength converter including a fluorescent substance excited by light emission from the LEDs to emit fluorescent light, and a light guide plate provided through the LEDs and the wavelength converter and configured to take in, through an end surface thereof, synthesized light of the light emitted from the LEDs and the light emitted from the fluorescent substance to release the light from a light emission observation surface side.